1. Field of the Invention
This invention relates to a modified and improved refrigerant recycling refrigeration system or a retrofit alteration to an existing refrigeration system that enhances the system's cooling efficiency. Between an outdoor condenser and an indoor evaporator, a sub-cooler is provided including, immediately before the sub-cooler, but still within the high pressure liquid refrigerant portion of the system, a high flow, low pressure release check valve that serves as an incremental expansion device to cool partially the high pressure liquid refrigerant before the refrigerant enters the traditional expansion device immediately prior to the indoor evaporator.
2. Description of the Background Art
Devices relying on standard refrigerant recycling refrigeration technologies have been available for many years. Heat pump devices, having both cooling and heating capabilities, are included within the general scheme of the subject invention, however, the subject device relates preferably to refrigeration systems. Within the limits of each associated design specification, heat pump devices enable a user to cool or heat a selected environment or with a refrigeration unit to cool a desired location. For these heating and cooling duties, in general, gases or liquids are compressed, expanded, heated, or cooled within an essentially closed system to produce a desired temperature result in the selected environment.
Within the plumbing that couples the various refrigeration or heat pump components are three devices of particular import with the subject device. First, check valves are traditionally employed to prevent the backflow of refrigerant. For a heat pump, often check valves are configured to direct refrigerant down a desired path during the cooling cycle and a significantly different path during the heating cycle. Several types of check valves exist. A common check valve has a spring controlled gate that increase its resistance to refrigerant flow as the spring is displaced from its rest position. Gravity check valves function by having a ball or similar object forced by gravity into a receiving seat to block reverse flow of the refrigerant.
Second, expansion devices serve to divide the high pressure side of the system from the low pressure side of the system by feeding the liquid refrigerant to the evaporator at a rate that, hopefully, optimizes the efficiency of refrigerant vaporization. Therefore, the refrigerant pressure drops significantly across the expansion device and the flow of refrigerant is regulated or decreased to a desired level. Automatic (constant pressure), float and surge chamber (constant liquid level), and, preferably, thermostatic designs represent the three major types of expansion valves.
Third, traditional sub-coolers partially cool the refrigerant prior to the expansion device and subsequent evaporator. Such refrigerant cooling has been shown to increase the efficiency of the heat transfer within the evaporator. Various types of sub-coolers exist, but the most common form cools the refrigerant by drawing in cooler liquid to surround the warmer refrigerant.
Concerning existing references, specifically, U.S. Pat. No. 3,024,619 relates a heat pump system having an additional row of finned tubes on the condenser. Due to a first associated check valve, the additional finned tubes act as a sub-cooler during a cooling cycle. When the system is run in reverse direction for heating, a second check valve passes coolant through the auxiliary coil thereby increasing heating capacity during the heating cycle without adversely affecting cooling operation. No direct monitoring coolant temperatures or pressures are associated with the regulation of this process.
A reverse cycle refrigeration system is disclosed in U.S. Pat. No. 3,365,902. The apparatus acts as a heat pump or as a system having a normal refrigeration phase and a hot gas defrost phase. A set of heat source coils forming a distinct refrigerant circuit is separate from the condenser coils but contained in a common fin bundle with the condenser coils.
U.S. Pat. No. 3,537,274 provides a dual evaporator refrigeration system. The system permits alternate connection of the evaporators for cooling while using the liquid refrigerant as the source of heat for defrosting the disconnected evaporator. There are two separate evaporators and a four-way valve for alternately connecting one or the other evaporator to the outlet side of the expansion device. The other evaporator is connected in the liquid refrigerant flow line so that liquid refrigerant passes through it. This liquid refrigerant serves as the source of heat for defrosting the evaporator not being used. As the four-way valve switches, the actions of the evaporators switch.
Disclosed in U.S. Pat. No. 3,918,268 is a heat pump with a frost-free outdoor coil. A heating means is associated with the normal outside coil to prevent the surface temperature of the outside coil from falling below 32.degree. C. Means are provided to prevent liquid floodback into the compressor when a changeover occurs from heating to cooling.
Described in U.S. Pat. No. 4,171,622 is a heat pump including an auxiliary outdoor heat exchanger acting as a defroster and sub-cooler. Located underneath the main outdoor heat exchanger and connected between the indoor and main outdoor heat exchangers is the auxiliary exchanger. During cooling the auxiliary exchanger acts as a sub-cooler and during heating it functions as a defroster for melting a block of ice that may have accumulated under or within the main outdoor heat exchanger. FIG. 1 indicates a check valve after the outdoor heat exchanger and prior to the sub-cooler, however, this check valve is merely to prevent, during the heating operation, the passage of refrigerant, thereby directing the refrigerant into the capillary tube (see column 4, lines 65-68).
U.S. Pat. No. 4,173,865 relates an auxiliary coil arrangement for a heat pump. The auxiliary coil is connected in parallel refrigerant flow arrangement with the expansion device of the heat pump. Standard check valves are provided to permit the auxiliary coil to function as a sub-cooler when the associated heat exchanger functions as a condenser.
Presented in U.S. Pat. No. 4,266,405 is a heat pump refrigerant circuit to reduce the time length of defrost cycles in contemporary air-to-air heat pumps. This reduction is accomplished by having two parallel refrigerant circuits connect the reversing valve to an outdoor coil. To regulate the direction of refrigerant flow, standard check valves are included.
A thermosyphon coil arrangement for a the outside unit of a heat pump is described in U.S. Pat. No. 4,449,377. When the heat pump is operating in the heating mode, the refrigerant flow is controlled by thermosyphoning action. Further, the coil placement and refrigerant flow are arranged for an outdoor unit so that the coil operates in an optimal thermosyphon fashion in the heating mode.
U.S. Pat. No. 4,553,401 discloses a reversible cycle heating and cooling system. Introduced is an auxiliary outdoor heat exchanger that is coupled with a water source for enhancing the capacity and efficiency of the system to transfer heat to the refrigerant during the heating mode at low outdoor ambient temperatures. A traditional check valve to water cooled refrigerant concentrator is indicated in both the cooling and heating cycles of the device.
A capillary tube-type expansion device for a heat pump is explained in U.S. Pat. No. 4,563,879. To regulate the device, a control unit detects the temperature of the outside air and the discharge water temperature of a water-cooled heat exchanger and applies a suitable control signal to an electrical expansion valve.
An apparatus for enhancing the performance of a heat pump is given in U.S. Pat. No. 4,761,964. First and second auxiliary coils are heated with associated radiant quartz heating elements. Outdoor temperature is employed, via a pair of thermostats, to regulate the operation of the quartz heaters.
Provided in Japanese Patent No. 38,143 is a heat pump type system having first and second units. The amount of cooling medium is regulated to provide maximum heating and cooling capacity.
Co-pending U.S. patent Ser. No. 07/660,141, filed on Feb. 21, 1991, discloses a supplemental heat exchanger system for a heat pump. Included is a receiver that acts to partially pre-cool the refrigerant by allowing the liquid refrigerant to expand slightly. Prior to the receiver is a check valve that prevents backflow during the heating cycle of the device.